Also known as glass fish and Red Sea Dwarf Sweepers, schools of these small fish are found not only in the Red Sea but elsewhere in the Indo-Pacific. They like shady places: wrecks, overhangs and caves. They feed at night on zooplankton.

Pygmy sweepers living in the Red Sea used to be known as Parapriacanthus guentheri, but it is now thought that there is just one species and Parapriacanthus guentheri is an obsolete name. They have light-emitting compounds in their guts, presumably gained from food they have eaten.